This invention relates to an ink-jet recording device used for printers, facsimile telegraphs, recorders, etc.
Generally known are various types of ink-jet recording systems to perform recording by ejecting drops of ink. As a typical example of such system, there is a pressurization-type ink-jet system in which voltage is applied to a piezoelectric element to distort the same, thereby applying pressure to ink to eject drops of ink. Such ink-jet system may be classified into two types; a pressure-pulse type system to apply voltage to a piezoelectric element only at recording and a pressurized and electrostatically deflected type system to charge-deflect a train of droplets into which a jet stream continually spouting under constant static pressure is split by the oscillation of the piezoelectric element. Referring now to the drawing of FIG. 1, there will be described an example of the pressure-pulse type system.
Pulse voltage of hundreds volts is applied between an electrode 2 and a metal plate 3 disposed respectively on both sides of a piezoelectric element 1 by a pulse generator 4. By the impression of such voltage, the central portion of the piezoelectric element 1 is distorted so as to project in the direction of arrow A to apply given pressure to ink body 6 in an ink chamber 5. By such pressurization, part of the ink body 6 is fractionized into drops and jetted from a nozzle 7. When a pulse signal from the pulse generator 4 falls, on the other hand, the central portion of the piezoelectric element is restored so as to move in the direction of arrow B to produce negative pressure in the ink chamber 5. As a result, ink is automatically fed into the ink chamber 5 through an ink supply inlet 8. By repeating such operation, the drops of ink are successively jetted out from the nozzle 7 for recording.
In the above-mentioned ink-jet recording device, pressure produced by the distortion of the piezoelectric element 1 in the direction of arrow A is applied not only toward the nozzle side but also toward the ink supply inlet side, leading to an entire loss of pressure. Accordingly, if ink is jetted from a nozzle with an inner diameter of approximately 50 .mu.m by using a disk-like piezoelectric element of 20-mm diameter and 0.2-mm thickness and a metal plate with the same thickness, for example, impression of pulse voltage of 300-V peak value will not be able to eject ink drops or to produce low frequency of an ink jetting.